Why do 適当 and いい加減 refer to both considerate and inconsiderate things?

Question

I understand that 適当【てきとう】 can mean both "appropriate" and "whatever/vague". How do you know 適当な人を教えてください means "please inform me of the appropriate person" as opposed to "please tell me about whatever kind of person you want"? Is this determined entirely by context?

Because 加減【かげん】 means "condition", いい加減 seems to be "good condition" -> only the "reasonable" definition comes naturally. Yet using it to mean "irresponsible" is standard (いい加減に仕事をするな), except when you tell people いい加減にしなさい. Where did that come from?

I saw this question in 日本人の知らない日本語 but no explanation was given. I am living in Japan but none of my Japanese friends can explain it either.

Answer 1

Since no-one has tackled the question in the heading, let me give it a try. This is speculation on my part, so if someone can knock it down or back it up with evidence, please do.

Consider a similar sort of construction, 都合が良い:

• 都合の良い日 = a convenient day.
• "都合の良いことを言うな" = "Don't say things that are convenient to you!" (translation intentionally unnatural to lay bare the contrast)

That is, while sometimes 都合の良い can mean "convenient for everyone", at other times it can mean "convenient for one party at the expense of the other", a subjective rather than objective concept.

By analogy, the meaning of "いい加減な仕事をするな" might have an original interpretation something like "Don't do 'just enough' work! [Do more! Do the best you can!]" Similarly for 適当: "just right" in the sense that it is exactly what Person X wants, or "just right" in the sense that it is the result of Person Y doing exactly the minimum amount of work to get by.

Incidentally even if this is how we got the apparently opposite results from the same basic meaning, I think that the process is fossilized now so that the phrases just have multiple meanings.

Answer 2

You can sometimes explicitly differentiate between them.

In case of 適当, if you write or pronounce it テキトー (colloquial) then it will explicitly mean "whatever". If you put strong accent on てき and pronounce とう short (i.e. as opposed to トー), it will explicitly mean appropriate. In a formal written document, 適当 will almost always mean appropriate. In less formal documents, you have to rely on context.

In case of いい加減, if you pronounce it with strong いい and soft 加減, it will mean good condition. If you pronounce it with more accent on 加減, it will mean irresponsible. When it's written, using いい加減 as "good condition" is a bit archaic now. So chances are that it means "irresponsible".

It's also true that in many cases you have to rely on context though.